Method for the production of railway ties

Abstract

Durable, weather and an insect-resistant railway ties are fabricated by the co-extrusion into a die of at least one mixture comprising asphalt binder and aggregate and recycled plastic, optionally strengthened by fillers such as glass fiber or KEVLAR.

1. A method for manufacturing a railway tie having a first portion fabricated of a first composition and a second portion fabricated of a second, different composition, said first composition comprising 15% to 75% by weight of a first asphaltic component and from 85% to 25% of a first polymeric composition and said second composition comprising from 20% to 85% by weight of a second asphaltic component and from 80% to 15% by weight of a second polymeric component, each of said first and second polymeric component comprising a mixture of a recyclable plastic and a strengthening agent, comprising the steps of:
 (i) separately preparing and blending selected amounts of asphalt and plastic to produce a first blend having said first composition and a second blend having said second composition; 
 (ii) separately melting and processing said first blend and said second blend in processors operable to heat and feed said blends separately as composite asphalt plastic composition to pump means associated with a co-extrusion die; and
 (a) pumping the heated and semi-fluid first composition into a first section of a mold to form said core portion of the railway tie, and simultaneously injecting the heated and semi-fluid second composition into an outer portion of the mold to form the outer portion of said railway tie, or 
 (b) pumping the heated and semi-fluid second composition into a first section of a mold to form said core portion of the railway tie, and simultaneously injecting the heated and semi-fluid first composition into an outer portion of the mold to form the outer portion of said railway tie. 
 
 
     
     
       2. A method according to  claim 1 , wherein the recyclable plastic is a recyclable thermoplastic material. 
     
     
       3. A method according to  claim 1 , wherein said strengthening agent comprises a recyclable thermoplastic material reinforced by the inclusion of fibres, or reinforcing agents. 
     
     
       4. A method according to  claim 1 , wherein said strengthening agent comprises virgin or recycled polypropylene or a synthetic polymer, reinforced by the inclusion of fibres, or reinforcing agents. 
     
     
       5. A method according to  claim 1 , wherein said first asphaltic component, second asphaltic component, or both first and second asphaltic components comprise a mixture of asphaltic binder and aggregate. 
     
     
       6. A method according to  claim 1 , wherein said first asphaltic component, second asphaltic component, or both first and second asphaltic components comprise asphaltic particles such that at least 75% of the particles can pass through a 0.50″ mesh screen. 
     
     
       7. A method according to  claim 1 , wherein said first polymeric component, second polymeric component, or both first and second polymeric components comprise about 50% by weight of strengthening agent. 
     
     
       8. A method according to  claim 1 , wherein said first polymeric component, second polymeric component, or both first and second polymeric components comprise approximately equal amounts by weight of said recyclable plastic and said strengthening agent. 
     
     
       9. A method according to  claim 1 , wherein said strengthening agent comprises virgin or recycled polypropylene filled with glass reinforcing fibres. 
     
     
       10. A method according to  claim 2 ,
 wherein said strengthening agent comprises virgin or recycled polypropylene or a synthetic polymer, reinforced by the inclusion of fibres, or reinforcing agents, 
 wherein said first asphaltic component, second asphaltic component, or both first and second asphaltic components comprise a mixture of asphalt binder and aggregate, 
 wherein said first asphaltic component, second asphaltic component, or both first and second asphaltic components comprise asphalt particles such that at least 75% of the particles can pass through a 0.50″ mesh screen, and 
 wherein said first polymeric component, second polymeric component, or both first and second polymeric components comprise about 50% by weight of said strengthening agent. 
 
     
     
       11. A method according to  claim 2 ,
 wherein said strengthening agent comprises virgin or recycled polypropylene or a synthetic polymer, reinforced by the inclusion of fibres, or reinforcing agents, 
 wherein said first asphaltic component, second asphaltic component, or both first and second asphaltic components comprise a mixture of asphalt binder and aggregate, 
 wherein said first asphaltic component, second asphaltic component, or both first and second asphaltic components comprise asphalt particles such that at least 75% of the particles can pass through a 0.50″ mesh screen, and 
 wherein said first polymeric component, second polymeric component, or both first and second polymeric components comprise approximately equal amounts by weight of said recyclable plastic and said strengthening agent. 
 
     
     
       12. A method according to  claim 3 , wherein the fibres are glass fibres. 
     
     
       13. A method according to  claim 4 , wherein the fibres are glass fibres. 
     
     
       14. A method according to  claim 10 , wherein the fibres are glass fibres. 
     
     
       15. A method according to  claim 11 , wherein the fibres are glass fibres.